1. Field of the Invention
The present invention relates to a method of reinforcing a mechanical part, such as a turbine engine part, for example, the part being made by assembling together two portions, e.g. by diffusion bonding.
2. Description of the Related Art
In order to reduce the weight and the cost of turbine engine fan blades, they are generally made of composite material. Fan blades need to withstand high levels of stress and impact because of their speed of rotation and because of impacts against particles or foreign bodies that might penetrate into the air stream. That is why composite blades are protected at their leading and/or trailing edges by metal reinforcement adhesively bonded on the airfoils of the blades.
Document EP 1 574 270-A1 in the name of the Applicant describes a method of making reinforcement by superplastic forming and diffusion bonding (SPF/DB), the method consisting in:                bonding two metal sheets together by diffusion bonding in order to obtain a preform, portions of the sheets being covered in an anti-diffusion substance in order to prevent them bonding together in determined zones;        cambering and twisting the preform;        inflating the preform so that it is subjected to superplastic forming; and        cutting the preform to shape to obtain the reinforcement.        
That method does not make it possible to obtain accurate control over the inside shape of the cavity in the reinforcement. In particular, the junction zones between the sheets form stress concentration zones and crack starter zones that weaken the reinforcement.
In order to improve the mechanical behavior of the reinforcement, a method of making metal reinforcement is proposed in patent application FR 10/51992, filed by the applicant and not yet published, which method consists in:                shaping two metal sheets by die stamping so as to make them approximate the final shape of the reinforcement that is to be made;        positioning the two sheets on either side of a core that reproduces the inside shapes of the suction side and of the pressure side of the reinforcement;        assembling the two sheets together about the core in leaktight manner under a vacuum;        shaping the sheets on the core by hot isostatic compression; and        cutting the sheets to separate the reinforcement and release the core.        
The hot isostatic compression of the sheets enables the sheets to be shaped to match the shape of the core and makes it possible, in the junction zone of the sheets, to obtain a large connection radius, and consequently to avoid any zone in which stresses are concentrated or that have crack starters.
The resulting reinforcement has a solid zone for absorbing the energy of impacts against particles or foreign bodies, which solid zone is extended by two lips for pressing respectively against the pressure side and the suction side of the blade to be protected.
There exists a need to improve the mechanical behavior of reinforcement in order to protect composite material blades against ingesting heavy foreign bodies such as birds, but without that significantly increasing the weight of the reinforcement.